Higher demands are placed on ventilation ducts when it comes to large cross sectional areas with low flow resistance and withstanding sub pressure. Another demand is to fulfil requirements for fire resistance classification. A further demand is a high level of insulation capability, especially when the duct is used for heating or air conditioning purposes. Additionally there are economical demands on decreased costs for manufacturing, storing, transporting and installation.
From the same applicant the basic technology is known, see WO 2013/043100 and WO 20133/043101.